Temperature induced de-polymerization in TDAE-C60

The phase change due to the polymerization of the ferromagnetic tetrakis-dimethylamino-ethylene (TDAE)-C ₆₀ has been reconfirmed by applying pressures in situ up to P _c=7 kbar in an ESR cavity. This transition is irreversible and the phase above P _c is stable even after releasing pressure. The pressure-dependent g-factor indicates the revival of the TDAE ⁺ spins. Moreover, the ferromagnetism disappears simultaneously at P _c . The de-polymerization of the polymerized (pressure-released) crystal has been confirmed for the first time by the high-temperature ESR study. This transition is also irreversible and the polymer phase is stable up to 470 K. The de-polymerized phase is considered to be the original ferromagnetic one.